Designing and Building an Expedition Vehicle Part 1

Designing and Building an Expedition Vehicle

Many people look to design and build their own expedition vehicles, in this article we shall take a look at what is involved as many projects are started, but less than 5% are actually finished for a number of reasons. Due to the widely varying requirements of the individual it is best to treat this as a “generic article”, but one which shares all the basic rules of planning and building, or converting an off road vehicle to an expedition vehicle.
Before even buying a vehicle it’s prudent to plan very carefully and in great detail as this may influence the choice of vehicle you purchase for your intended project, and we will begin with this process. No two people will have the same requirements and no two vehicles will be alike in specification, and many vehicles may be fitted to a basic specification and will be upgraded at time and funds permit, upgrading needs planning so you purchase the right equipment first time.
Planning falls into three categories, these are the essential items you have to have on your vehicle, the “would like” items you would like to have in addition to the essential items, and the type of travel you intend doing, remembering your travel could change for many reasons. My preferred choice is to break these sections down into individual sections for ease of reference as these could influence other areas of your vehicle, or your actual vehicle selection. Good planning goes further than just breaking down the individual sections as it analyses them in microscopic detail. How many people consider the volume of water they require but forget to add a contingency for emergencies such as breaking down in a remote area, or the actual weight of the water tanks and water, these are the depths of detail you will need to go into for a successful expedition vehicle conversion.
Essential Items
AccommodationCooking Electrical Heating Refrigeration
Safety Systems Storage Ventilation Waste WaterClean Water
If we look at the essential items main headings we can begin to break them down into sub-sections and then individual items, at this point the research into what its specifications, weights, sizes, consumption, and storage can be considered. If we take the main heading of electrical alone we can break this down as follows:
Auxiliary Batteries FridgesLighting Main batteries Mains Hook up
Split ChargingPower PointsConsumption
If we begin by looking at our vehicles usage we see how this affects our basic sub section of auxiliary batteries, are we going to be away from the mains for several days? Are we going to be totally reliant on the vehicle for our power? From here we can make decisions. What will be permanently powered? How much lighting do we need? How much power consumption have all these items? What will be permanently connected and drawing continual power? What will draw intermittent or variable power?
Will the vehicle include an intelligent mains powered charging system to maintain the batteries and systems if and when the vehicle may be stood for a prolonged period between use.

All these factors determine the size and output of the auxiliary power supply from our batteries as does “will we be travelling every day” and recharging them or will we be away from civilisation for a number of days and not running our vehicle.
If we make a few calculations we can determine our auxiliary battery pack size, we have a fridge continually running and it draws an average 4 amps per hour it will need 4 amps X 24 hours which equals 96 amps of power per day. If we are away from the mains and totally reliant on our batteries for 5 days we need 480 amps of power just to supply the fridge for five days, we are now beginning to determine the size of our battery pack. If we factor in the additional electrical loads such as lighting and we have decided on fluorescent lighting which draws 2 amps per hour, per light, and we have three fitted, and they are switched on for around 5 hours per night we can amend our calculations. With three lights switched on for 5 hours per night drawing 2 amps each we can calculate that 2 amps X 3 lights = 6 amps per hour which when multiplied by 5 hours per night equates to another 30 amps of consumption from our batteries per night. If we add this to the 480 amps we need a minimum power requirement of 600 amps from our batteries for five days and four nights. If we do this with every other electrical device we may run such as a radio, television, water pumps, charging portable appliances, and anything which uses electricity this figure will be considerably higher.
This level of breakdown and detail is repeated for every section, and its importance cannot be overemphasised if costly mistakes are to be avoided; remember, correct planning is the key to good vehicle design.
We can work out our alternator amperage and just how long the electrics can run without the engine being run, and when we need to run the engine, and how long for to recharge the batteries.
Now we can make informed decisions, if we assume we have two rechargeable lanterns which take three hours to charge and provide 8 hours of light per charge, and they take 500 milliamps (0.5 amps) per hour charging each we can conclude another 3 amps will be drawn charging these. If we also factor in running a laptop or charging mobile phones and/or portable two way radios we see our consumption rising, and this is where the details really count as this level of scrutiny really counts. If we look at other variables such as travelling to hot climates we can reasonably conclude our fridge power consumption will rise as it will be working harder, this may rise from our average 4 amps to around 6 amps during the hot days and drop slightly at night. Already we are approaching a power requirement of around 800 amps from our batteries.
If we look at batteries for our vehicle we can base our requirement of 800 amps and to get this we can obtain four X 200 amp hour leisure batteries to connect in parallel to obtain our power requirement of 800 amps. If we look at various battery manufacturers we can obtain the technical specifications for these batteries, if we look at the weight and we see they weigh 12 kilograms each we have just added 48 kilos of weight just with the batteries which meet our requirements. We have other options, we could reduce our power consumption by switching to a hand pump for our water, switch from fluorescent lighting to LED lighting, have a rechargeable radio which is charges while the vehicle is on the move, but we have options to consider. If we factor other things such as “would like” items such as a gas heater which has an electrically powered fan, or water pump for radiators; or water heaters we can conclude our electrical consumption will rise even more.
Clearly we have made the point that everything influences something else, or is influenced by something else, and every tiny detail needs considering before we even decide upon a vehicle. We also have to remember that this not only influences our choice of vehicle but our original vehicle choice may not accommodate all of our necessary items, or it may not carry the weight.
One word of caution: never rely upon manufacturers specifications for power consumption, particularly with fridges as they often consume much more power than the manufacturers’ state and this is because power consumption is a major selling point. Manufacturers do not lie as they merely test their products under perfect laboratory conditions to lower their power consumption as they will consume much more power when they are full of food and working in much higher temperatures than in the laboratory. Several years ago we tested several fridges and found the manufacturers power consumption figures excessively low, we tested in actual working conditions and I would suggest doing the same with all portable electrical appliances. Fluorescent lighting is another prime example as its load is much higher when starting up when they are switched on.
Going into this amount of detail with every single item on a vehicle means you have a “generic “specification from which to work, you know your power consumption, the weight, size, and capacity of everything, and have accounted for every external influence.

From this basic planning schedule you can select a vehicle which has the room and load carrying capacity for your basic schedule of works, knowing the weight means you can purchase a vehicle with adequate load capacity or be aware you will have to make upgrades. Normal upgrades for additional weight would be the suspension and braking systems and you can research the kits for such upgrades and compare prices and specifications for each kit which would be suitable for your needs, or have the knowledge to decide to upgrade or purchase a vehicle with adequate load capacity, and cost it accordingly.
Now we have the size, weight, and capacity of size of everything we can begin to look for a suitable vehicle to convert and fit it all into and work out how we can fit it all in, and narrow our choice of vehicle down to those suitable. Vehicles can be defined in three categories, those already with a suitable body, those with a body which needs modifications, and those which require a body to be constructed from scratch.
Vehicles with a body already fitted predominantly tend to be ex military vehicles used mainly as ambulances as these come with the four wheel drive and enough headroom to stand up in and work on casualties. Being a military specification vehicle often means they come with up rated components, under body protection and a host of readily available spares through military vehicle dealers or the vehicle manufacturers specialised vehicle departments, basically they are readily obtainable at reasonable prices. Many other types of vehicles are obtainable such as specials from the main vehicle manufacturers; most of the larger manufacturers do a 4X4 version of their vans which means 4 wheel drive and a choice of body styles and carrying capacities. Other specialised vehicles are available from a variety of sources and are not as readily available as those from the mainstream manufacturers. This category of vehicles is the easiest to modify for an expedition vehicle as most of the bodywork is already in place, it’s more a case of fitting them out to your requirements and fitting what equipment you need in a suitable location on the vehicle.
Moving to the next category we find vehicles with a body which is unsuitable, but can be converted to suit out needs, these tend to be modified 4X4’s which are fitted with a plastic top to form a higher roof than the normal variant of the original vehicle. Generally the bodies are cut and raised to allow a reasonable head height or a plastic high top roof is sourced from the breakers and used to replace a lower roof variant if the vehicle comes with optional roof heights. Many manufacturers supply base vehicles for conversion, the main vehicles are Land Rover, Range Rover, Mitsubishi Shoguns, Toyota Land Cruisers, Ford Explorers, Isuzu Troopers, Nissan Patrols, Jeep Grand Cherokee’s and many more worldwide. Converted vehicles tend to be the larger 4X4’s as they come in LWB (long wheel base) versions, durable four wheel drive systems and rugged and durable engines and have the space and load capacity for a variety of conversions by specialised manufacturers or convertors. Many of these vehicles are used for specialised roles such as small ambulances, compact rapid response 4X4 fire engines, work vehicles, military vehicles, or even rescue vehicles for a variety of industries. Having the base vehicle as standard as possible means components are readily available and reasonably priced for much of the vehicle and this makes them attractive for further modifications by those with, or access to the necessary skills.
Our last group of vehicles are the chassis cabs and these are the easiest to custom build into an off road expedition vehicle as you have a blank canvas from which to work, you can buy cheaper, standard components and make your bodywork fit around anything protruding. You do have to make, or have a body made. This class of vehicle is best left to the experts or experienced convertors unless you can buy a second hand body for your vehicle, but offers a greater opportunity to customise or purpose build the vehicle to your exact specifications. Base vehicles come in a variety of guises and most will be a chassis cab from a specialist dealer or second hand, predominantly from the military market.

What Type Of Expedition Vehicle
This is an important consideration as it influences many things, if you prefer to camp then all you need are enough seats for the occupants and enough space for your camping and expedition equipment, a 4X4 crew cab pickup would then suffice if it carries your kit. This would give you 4/5 seats and a reasonable space for most camping equipment and additional water, fuel, and gas you would need for several days. Alternatively a hard bodied vehicle such as a standard or ordinary LWB 4X4 may suffice as you will not be living inside the vehicle at any time. Simple plastic storage boxes will suffice for most of your kit and these can be stacked in the rear and lashed in position as most vehicles have lashing points inside them. Everything is inside the vehicle and in reality there is often no need for additional carrying capacity unless you intend being away from civilisation for many weeks, and, in many cases a full size roof rack will provide the additional carrying space for the additional kit needed. Basic vehicle modifications are all that may be required, under body protection, long range fuel tanks, two spare wheels, additional lighting, charging points for rechargeable equipment, and a GPS/navigation system would be all most people would need.
Moving on from this we could look at two people wanting basic accommodation without the hassle of erecting a tent every night and packing it away every day, in this case a roof tent may suffice for your needs, and the freed internal space could house the roof carried equipment. Roof tents offer basic accommodation and lack anything but sleeping space and enough room to dress so consideration for personal hygiene and cooking are an important consideration unless you are in a remote and warm environment. Here in the UK we cannot guarantee the weather and with regular rainfall through the summer a roof tent could leave people cooking in the rain, at the very least a cover needs improvising for such conditions along with a windbreak. This needs to be high enough to cook under without struggling and generally this means being able to stand up under it and large enough to cover a small table and at least two chairs.

Many people prefer the additional comfort of sleeping inside a vehicle instead of outside and in many areas of the world this offers a little additional security or protection from local animals or predators (some human) which may be venomous. Hard body vehicles are best suited to this and these would predominantly be ex military 4X4 vans or vans from the main commercial manufacturers who supply a 4X4 variant. These vehicles do need converting and do allow reasonable space for sleeping inside with folding beds and the option of having a basic, built in cooker for inside cooking away from the elements, and many offer the opportunity to fit long range fuel tanks or water tanks. Careful design is essential to incorporate your equipment, but most things can be fitted, although many items may have to be bespoke to fit the available space which can be a downside or costly, particularly under floor or chassis mounted water tanks. With a hard body 4X4 van or large 4X4 it is fairly easy to fit an elevating roof for more headroom, and many ideas can be adopted from modern boats, motor homes or caravans as well as internal fitments.
Coach or scratch built vehicles are the hardest vehicle to convert for the home convertor as building a vehicle body is something many people feel is beyond them and unfortunately many people do not attempt this for these very reasons. Anyone with reasonable DIY or motor vehicle skills can build their own body with very few tools if they know how to approach it, and I feel more people ought to build their own bodies. These can be built to your own design, incorporate adequate headroom for standing, allow fixed items such as beds, cookers, fridges, sinks, water and fuel tanks, and cupboard space to be exactly where you want or need them for maximum practicality. These coach or scratch built bodies are better built on larger van chassis, or smaller lorry chassis as they offer the larger payloads and their off road mechanicals are very durable when carrying weight, the most popular chassis sizes are the 5-7.5 tonne chassis. Building your own body means you can customise it at the design stage to incorporate all your fitments as you have their dimensions and weights, and shape your body away from the boxes we commonly see. You can incorporate niceties such as insulation to keep the body warm in cold climates or cooler in hot climates, sleek bodies rather than ugly boxes, and a range of things you would not normally consider; basically it’s as flexible as your imagination, finances, and ability.

Planning The Layout
Many people struggle with planning the layout of a vehicle and not everyone has the benefit of 3D Cad software that I have, and cannot generate scale drawings in 3 dimensions which can be very detailed to the point of dimensioning every item to scale, and seeing the final layout. Worry not, there are ways round this and all it requires is a little imagination, a tape measure, and some basic materials and skills to generate a full size layout of your vehicles body, or just the floor.
Often we have numerous cardboard boxes left from packaging, save these and lay them out on the floor of a garage, workshop, or shed, measure the internal sizes of a range of vehicles and transfer the measurements to this cardboard, this will give a floor plan in full size. If you have a surplus of cardboard you can erect some sides as well, just stick them to the floor plan with a reasonable degree of accuracy. Refer back to your generic specifications and the equipment you intend to fit, look at the dimensions and cut cardboard to the size of the manufacturer’s sizes and place it in the floor plan, if it does not fit you simply move it around until it fits neatly somewhere. If you do this with all your items you intend fitting you will be able to install your cardboard templates to determine which the best layout is for you, and ensure all your equipment fits. Most manufacturers of equipment show scale or dimensioned drawings of their equipment on their websites, and retailer’s sites often carry this information also.
If we take this one stage further we can make a full size mock up of a vehicle body by using any number of materials, my preferred choice is thin timber lat’s as they are light, easily connected, and let the light through, yet replicate a skeleton vehicle bodies internal space. Timber lat’s are nothing more than thin pieces of timber approximately 40 X 15mm and available from anywhere, or just cut from planks which are 15mm thick, with a circular or bench saw. Building a full sized mock up gives the true impression of exactly what space is available, and your fixtures and fittings can be made as full sized items as well. Polystyrene foam used as packaging material is light, easily cut with handsaws, and bonded together to form full sized items. Many household materials can be used to produce full sized replicas of equipment to its exact size, and having these fitted in the mock up means you can judge the height of items as well as many items will be different heights. 3 dimensional modelling in real size also allows for intrusions into the living space from items such as wheel arches or fuel filler pipes, and allows you to select specific items.
3D modelling eliminates many mistakes people commonly make by assuming items will fit when they won’t, and it allows accurate measurements to be taken for the fabrication or manufacture of framing or other fitted equipment. It allows the layout of pipe work, wiring, and ducting or vents for various items to be determined, then drawn onto a plan; at this stage it allows for photographs of the layout to be taken for future reference and stored electronically on a computer. Having a visual reference makes life much easier for beginners and experienced vehicle convertors alike. Many people make changes to their designs as conversions take time and people change their minds, they may like a newer, updated item than originally specified or equipment may have been discontinued in favour of newer models by a variety of manufacturers. Many items need a specific amount of room for venting or air inlets to be installed, these would normally be fridges or cabin heaters running off fossil fuels, and this is a safety specific issue, 3D modelling allows you to check the room and install equipment safely. Where there is insufficient room you can modify your design to allow for such issues.
3D modelling allows the builder to answer many questions, do I need a folding or fixed bed, will it fit, will there be room for a cooker, fridge, sink, and drainer, and will I have the room to move around the vehicle with them all installed. 3D modelling allows these questions, and many more to be answered and any mistakes to be highlighted at this stage, and not after you begin the conversion, at this stage it costs time and a little more thought, after beginning the conversion it costs you time and money to rectify any layout errors.
3D modelling can be used for exterior fitments, this allows mock up’s of items such as water tanks or batteries to be made from polystyrene, will these fit in the allocated space or do you have to get a different design or shape of tank. 3D models allow these questions to be answered, manoeuvring a lightweight model into position is much easier and cheaper than buying the real thing and finding it doesn’t fit, or its filler or outlet pipes foul something else, and they can determine mounting brackets locations. Fitting a mock up will allow the positions of other items to be determined such as access hatches and wiring, it’s crucial to know there locations before you begin cutting holes onto bodywork so you get it right first time and don’t spend time and money correcting silly, avoidable mistakes. It takes a few seconds to make a silly mistake, and many hours to correct it, hours which can be spent doing other things.
Many vehicle convertors may well purchase equipment as they go along, this spreads the costs of expensive items which may be built up over many months, if you have any items you can use your 3D model to actually locate them in their correct positions. This saves cutting and gluing mock up’s in polystyrene or cardboard, and you can judge them more accurately, particularly any intrusions into the remaining space from catches or handles. There is nothing more inconvenient than finding a sharp edge to catch yourself or your clothing on, and that offending item is in a place where you walk around your vehicle regularly, or that a door won’t open because it fouls some other fitment.
If you have stuck cardboard together and formed an accurately sized floor plan you can use this to mark the position of any intrusions for wiring, piping, gas lines, and anything else you may require, use different coloured wax crayons for this. You can lift your cardboard mock up floor and stick it to a garage or workshop wall for easy reference once you begin your conversion; colour coding makes it easier to identify each item from a distance. If you have measured and made an accurately measured floor plan in cardboard you can even measure it and mark crucial dimensions onto it.
Now you have an accurate floor plan you can work out the location of many ancillary items, where are your batteries going to fit, where the location of your gas bottle/s are, are you going to fit a mains power unit, and will all this weight be located in one spot in the vehicle. Having such a floor plan allows you to balance the weight of any additional items so you don’t have all the heavy items located in one place, and allows you to modify your proposed layout if necessary.
Now you have worked everything out accurately you can specify every piece of equipment you intend fitting, you can specify a make and model for everything and price it up from numerous suppliers. You can include this detail on your plans and take a generic specification to a fully detailed specification with a full cost. The golden rule is “making the mistakes with cardboard and not with real equipment” a rule I have always followed.
An Actual Build
This is an actual vehicle we built, the owners were experienced off roaders and expedition vehicle veterans, and they wanted a replacement for their older vehicle, and one which would offer more space and flexibility then their current one. Rather than give the full specifications we will give the basic requirements and the specifications will be seen as we progress through this section. Being a couple meant the vehicle was primarily a two berth vehicle, and was to be used in cold and hot conditions, which meant an insulated body; and it had to cope with occasional family visitors, as well as be totally self reliant for up to three weeks. This vehicle had to have a lifespan of at least three years and preferably longer; and fully fitted, had to remain below 7.5 tonnes due to constantly changing European regulations which are trying to ban drivers driving in excess of 7.5 tonnes on a standard UK license.
Having an experienced couple meant a lot of the design work could be omitted, they knew what they wanted, it was just how it was going to be laid out which caused the most minor problems, so the design was laid out in 3D cad so it could be seen to scale. Having much of the equipment they wanted also meant we had the dimensions to hand as they had been buying for around a year prior to the build, this virtually gave us the generic specifications and the weights of most equipment. Based upon this we concluded a 7.5 tonne chassis would be the best option as their earlier 5 tonne chassis would not carry the weight of the equipment, along with the fuel and water for extended trips of three weeks away from any services. Their previous 5 tonne Iveco 4X4 chassis had proven reliable and durable, but electronics problems with silly items such as the oil level sensors, and other petty things which did not stop the engine, but lit up the dashboard, had begun to niggle them.
Looking around the marketplace yielded many 4X4 chassis ranging from 5-7.5 tonnes with four wheel drive; and even some conversions which were started, but not completed, and many were dismissed as poor quality conversions undertaken by amateurs. None of the vehicles had lightweight bodies, and like their previous vehicle, had uninsulated bodies which were not suitable for their chosen future venues; and many were aluminium. As we all know aluminium is an excellent conductor of heat and cold, not something people want, moving from an oven in hot climates to a fridge in cold climates. Having a generic design on the computer meant we knew what chassis lengths we were looking for, and the best buys were ex military vehicles as they had the chassis lengths, under body clearance, and lots of heavy duty kit fitted as standard. Engines were crucial, it must have a world market engine so spares could be sourced in remote locations, or only a couple of days away if the vehicle broke down and required parts, a 7.5 tonne 4X4 ex military vehicle with a Cummins engine was sourced. This met the requirements as the engine was a detuned variant of a standard engine, it was noted for its durability and longevity, and being durable in a higher state of tune meant it would not be overstressed in its application, a deal was done on the vehicle, and purchased. This vehicle came with the 6 speed overdrive gearbox instead of the normal 5 speed unit, and had a centre diff lock and rear axle diff lock as standard.
Once back in the workshop (my barn) work began on the chassis cab, this involved a full evaluation of the vehicle while it was easily accessed, all under body protection panels were removed and work began on the basics. Every suspension, steering, and braking component was examined, all the grease nipples were replaced with new items and everything was fully greased with new grease, and the engine/chassis were cleaned with de-greaser and jet washed. Once this was done all the oils were drained and replaced and the cooling system was cleaned with an industrial cooling system cleaner and flushed until it was as new. Work began on the engine modifications, this included fitting an up rated; and more durable aluminium radiator, an up rated power steering cooler, and fitting an intercooler as it was a turbocharged, none intercooled diesel engine. Being an up rated item meant the coolers were much stronger than the original coolers and could stand more off road abuse, they were flexibly mounted on special rubber mountings to give them more flexibility if impacted by something heavy. Water pipes on the engine were replaced with silicone hoses and colour coded for ease of identification. Oil coolers were next on the agenda and this involved fitting a small oil cooler with a thermostatically controlled output to prevent overcooling the oil in cold climates, and with sufficient cooling for when it worked in hot climates.
Work began on the engine, another alternator was fitted, and the original alternator was replaced as this was a low powered unit, this gave two high powered marine alternators, being marine units meant they were also waterproof. All they needed was an annual clean and the waterproofing topping up with a special waterproofing spray simply sprayed into a cold alternator, they would work underwater and are much more durable than a standard vehicle alternator on a 4X4. Engine pulleys were changed so every item was switched from a single belt drive to twin belt drive, again it was a little security if a drive belt broke in an awkward location, and industrial drive belts were fitted in preference to automotive drive belts. Twin agglerometer/fuel filters were fitted to the chassis, agglerometers remove water from the fuel before it gets to the normal fuel filter and having a clear bowl allows a visual check of how much water is in the filter without having to drain it or remove the filter. Having twin units was for the twin fuel tank set up which was to be fitted to the vehicle, this would allow one fuel tank to be used, or the other fuel tank if one was contaminated with fuel of poor quality, or the often found diluted fuels in many countries. These were located on the inside of the chassis for easy viewing from the rear of the cab as their bowls are acrylic for a visual examination. They merely had a changeover valve fitted in their individual outlet pipes to the diesel injection pump and could be quickly changed over if a fuel tank was contaminated or empty. With the engine work done it was masked up and sprayed with an industrial paint, then the service parts were replaced and new glow plugs were fitted for security and reliability. Next came two water manifolds on the engine, one was for the feed of hot water from the engine, the other was the return, each had been cast and machined at home and they were fitted with six 3/8th BSP ports as everything was to be standardised to 3/8th BSP threads for ease of maintenance. Commercial/industrial variants of this engine have a twin thermostat set up, one was obtained and fitted; this is basically one large external housing containing two thermostats with slightly different temperature thermostats, if one fails the other will still work. Once again this was a reliability modification for the vehicle, the cooling system was now filled with a 50/50 mix of long life anti-freeze and distilled water, and Bars cooling system repair compound as this seals leaks and contains a cooling system lubricant to lubricate moving parts. It was at this point we decided to replace the water pump with a new item, again for reliability, so the system was drained and a new pump fitted, the removed item was found to be fine and lubricated and kept as a spare item. The system was then refilled to protect it from corrosion.
Behind the cab became the next focus as everything was stripped off and the entire chassis was cleaned with a wire brush on an angle grinder to remove some of the rust which had accumulated during its working life. This was now measured very carefully to ensure everything in our generic specification could be fitted, and a few amendments were made to formulate our final specification for the chassis.
Now the fuel tank was fabricated, this was essentially a large saddle tank which sat on top of, and dropped between the chassis rails, it was basically one large tank which was divided internally to give two tanks, and carried a combined 130 gallons of diesel in both tanks. This also incorporated two smaller integral 15 gallon fuel tanks for the vehicle as it was to be gas free, and this additional 30 gallons would power the diesel cooker and diesel heating; gas was not an option as the channel tunnel authorities had caused previous headaches when they used it in preference to ferries. Vents for the fuel tanks were run to a filtered housing to prevent the ingress of dust and water and were simply a cleanable performance component the boy racers use, it is cleaned and simply oiled, so suitable for such applications, and simple. Fabricating the tank was fairly straightforward as we had a clear chassis, but it involved removing one cross member and replacing it in a better location to support the fuel tank and the battery housing. Aluminium was chosen for all the tanks as it was lightweight and not prone to corrosion as steel tanks are, and they are not prone to stress cracking as stainless tanks are. Templates were made in sheet timber to ensure it sat correctly on the chassis and cleared the gearbox, from this the two sides were cut with the plasma cutter, one side was drilled for the fuel suction and return pipes to exit, and for the tank fuel heaters to be installed. On one side of the tank was welded the centre divider to partition the tank into two separate fuel tanks and the tank bottom was welded in, bushes were machined and welded into the tank bottom for the drain plugs. Both sides were welded on to the bend where they sat over the chassis, and then the other side was welded on. Leaving part of both sides and the top off allowed the tank to be fully TIG welded on both the inside and outside for strength. At this point both sides of the tanks were filled with 10 gallons of water stained with food colouring and its height measured, this was repeated at 20 gallons, 30 gallons, and so on, and at these measurements the tanks were drilled. More bushes with 3/8th BSP threads were installed so they could have clear sight glasses installed to give a visual indication of the individual tanks actual contents if there was any failure of the fuel gauges, these sight glasses are commonly fitted to hydraulic tanks, and cheap to buy. They cost £0.30p each plus UK VAT, so cheap insurance. With this done the remaining parts of the tank sides were fitted and fully double welded and the tank could continue to be filled with the stained water to have a visual sight indication glass fitted at the appropriate height to correspond to each 10 gallons of fuel. At this point the fuel tank heaters were installed, the sides had been drilled for them and they were made from thick wall aluminium tube of 10mm diameter which was bent into a “U” shape and had the sockets welded onto them. They were slid into the fuel tanks and the sockets pushed into the holes, they were fully TIG welded in and a 3/8th BSP tap was run into the sockets to clear the threads from any welding distortion, which there wasn’t. The 15 gallon tanks for the heater and diesel cooker were installed, these were simply “L” shaped pieces of aluminium with slots cut into the top at one end, and this was a design feature as the 15 gallon tanks would always be filled first. Once filled the remaining fuel would run through the slots cut into the top of them and fill the fuel tank. Now the top was fabricated, this had a couple of unique features, these were the fuel fillers, in addition the inspection plates and apertures for the fuel gauges were added, and the vent pipes were added. This was installed and fully welded, and the fuel filler pipes were added, these were two centrally mounted fuel fillers to allow the individual tanks to be filled from a fuel pump on either side of the vehicle. In addition each central filler pipe had another filler pipe added to it which ran to its respective tanks side of the vehicle. This allowed the left tank to be filled from a fuel pump on the left hand side of the vehicle, and the right hand tank to be filled from a fuel pump on the right hand side of the vehicle, or both tanks to be filled from a pump, irrespective of side, through the central fillers. Vent pipes were now installed and the housing for the vent filter was fabricated and installed; temporary blanks were fitted to all exposed or open holes and the tank was pressure tested to 100 psi to ensure there were no leaks.
Now nearly fabricated, the tank was installed in the chassis, and it was to be mounted on several rubber mountings with two rubber mountings mounted in the chassis to prevent excessive sideways movement when the tanks were full. Mounting rubbers were installed in the chassis and on the newly moved cross member and the mounting brackets for the fuel tank were roughly located, the tank was adjusted to its final position and the mounting brackets were welded into position on the tank. Now the tank was removed and weighed and tested for actual capacity, it weighed 9 Kg as is, and its capacity was measured, the tanks held a combined 132 gallons for road use, and 32 gallons for the diesel cooker and water heater. With the tank removed it was drained and dried out and given an internal epoxy coating and a coat of epoxy paint on the outside. The tank was reinstalled in the chassis and everything was fitted to it. Fuel connections were made to both the agglerometers; water pipes were fitted from the water manifolds, wiring connections were made for the gauges, and everything was checked to ensure it worked.
Moving to the other side of the now moved chassis cross member, we measured and fabricated a battery box to contain eight heavy duty traction batteries, having a friend who owns a battery dealership helped us source the right batteries very cheaply. Batteries were rated at a massive 835 amps each, and being a traction battery meant they could stand the abuse of heavy discharges and also provide the starting power for the truck, without damage. They were split into packs of two service batteries for the truck, four batteries for the ancillaries, and two spare batteries for miscellaneous items as the wiring was to be a split loom for a variety of reasons. This left us with a massive capacity of 1670 amps for the truck batteries, 3340 amps for the auxiliary battery pack for running the body for sustained periods, and a further battery pack of 1670 amps for various items which were left running due to our split wiring design.
Fabricating the battery box to accommodate these batteries was straightforward and each set of batteries had a divider to separate the three battery packs, the box was aluminium and this is a good conductor of heat so it was insulated for cold climate operations. Solid insulation sheet was used to insulate the battery box and tiny ventilation holes were drilled and fitted with 4mm silicone pipes to drain any gas from charging and discharging. Wiring grommets were installed for the massive cables needed for these packs, and the massive marine alternators installed on the engine.
Moving back down the chassis gave us the location of the water tanks, once again the decision was taken to use two tanks instead of one single tank; in many places they travel to, or through, the water quality is not to a standard we take for granted in the UK. Having two tanks meant one could be used and the other tank could be filled and have water treatments added, then left while they worked and neutralised any nastiness in the water so it was drinkable. One internal 25 litre tank was also used internally, and mounted below the sink; in the event of the underbody tanks freezing or becoming damaged the vehicle would have a couple of days water stored, This tank acted as the main feed for the taps and the water heater which was to be fitted, and was simply filled by pumping water from one of the two underbody tanks. Tanks were obtained from a food factory for free, we were doing some work there and I asked if I could have them, once they found out they were to be re-used they obliged as they were very big into recycling. These tanks were cut down and re-welded using TIG, and the filler spouts, drain plugs, and apertures for the water pumps were fabricated and fitted, and the stubs for the vents were installed, once again brackets were made and fitted to the chassis to accommodate these tanks. Electric tube heaters were installed to prevent them freezing, these were thermostatically controlled with a manual override. Once again they were mounted on rubber anti vibration mountings, and the chassis was drilled to install the cross vehicle filler pipes, these allowed two fillers per tank, one on each side of the vehicle for ease of filling them. These tanks had a combined water storage capacity of 240 litres, plenty for several days and with a contingency if they became stuck in a remote location for several days. Tanks were insulated with a spray on insulating foam once they were installed, this would help prevent freezing in cold weather, and wrapped in thermal insulating blankets which generate slight heat if the temperature drops below 2 degrees centigrade. Power points were fitted between both fillers on each side of the vehicle to allow a water pump to be used to fill the tanks from water containers in the event of tap water not being available, this was a standard unit used on modern caravans.
Cross members were made to fit the body on, these were temporarily tack welded to the chassis to check their alignment, then adjusted where necessary, brackets were welded to the cross members and the chassis drilled through their already drilled holes. Bolts were inserted and tightened, and the temporary tack welds were ground off. Various other brackets were fabricated and welded to the chassis; these were for the grey water tank which was detachable, the spare wheel, and a filter assembly to replace the grey water tank which filtered out any solids, but let grey water drain onto the ground.
Finally a rear specially designed cross member was fitted to hold the hinged rear access door for the body and its drop down staircase which would be an integral part of the body; this would also be the rear bumper and house the LED rear lights, when manufactured.
Brackets were made to locate all water pipes, electrical connections, fuel tank connections, and anything else which needed protection, and these ran inside the chassis rails down both sides, and pipe work and electrical looms were made and installed loosely. Everything was fitted to the chassis to ensure it fitted and all connections were made, then everything fitted to the chassis was carefully removed to protect it prior to installing the body floor.
Making The Body
Making the body began with making the floor, for this we used SIPS panels as they are structurally bearing and highly insulated, SIPS panels are sandwich of a 2mm thick face of aluminium, a 62mm layer of insulation, and a 6mm thick birch ply. Two pieces were laid side by side and connected by bonding with the correct adhesive; these were the full length of the floor and the overlapping aluminium face was screwed using the correct screws. These were cut to width by trimming the prescribed amount off each side, then they were laid on their cross members and aligned and clamped onto position on their cross members. Pre-drilled holes in the cross members were used to mark out the holes for the floor, these were drilled and plastic mounting bracket’s were bonded onto position inside the drilled holes, these came with a tapped thread inside them. Once drilled and the inserts were inserted, and once the adhesive had dried, the floor was located on the cross members and bolted into position, this gave rigidity to the floor and allowed us to mark it out for the body framing.
SIPS or Structurally Integrated Panelling System are actually the composite panels which are used on the roofs of modern highly insulated buildings, also for cladding them.
Body framing was made from a material called Lite-Ply, this is epoxy bonded plywood which is very lightweight and generally used in the aircraft industry, as the owner of the vehicle owns his own woodworking business; he did them. They were formed using 4mm thick plywood laminated together using three pieces to stagger the joints and give a suitable thickness of 12mm for attaching the external body panels and internal linings, and they were 35mm wide to accommodate the various components in the cavity. The remaining longitudinal members were made in the same way and both were rebated so they would slot together easily to form an accurate wooden skeleton which could support itself, this was completely assembled to check the fit. With the skeleton assembled and accurately aligned the tapered back of the skeleton was made, and the front framing which was shaped to cover the battery box and partially cover the fuel tanks to offer some protection from the elements, but still allow access to both the batteries and fuel tanks. This was tapered at the front for added aerodynamic efficiency, and to blend into the cab roof which was to be cut off and also tapered for aerodynamic efficiency. With the skeleton fully made the floor was fitted permanently to the chassis on its anti-vibration rubber mountings and marked out for the wooden skeleton to be fitted, slots were cut with a router to a depth of 35mm and squared off to accommodate the skeleton. Fitting the skeleton was as simple as lifting it onto the floor and slotting it into the cut grooves, the alignment was checked twice for accuracy and the entire skeleton was lifted out and packed in the air with wood packing. All the grooves were filled with adhesive and the skeleton was dropped back into them, it was so light that two people could lift it easily and manoeuvre it into position, once located in the floor grooves the longitudinal members were quickly removed bonded, replaced, and clamped. The whole assembly was left for 2 days to allow the bonded joints to fully cure, this was more for a little security as it fully cures in 12 hours, but being a little prudent was in our minds at this crucial stage. With the wooden skeleton securely bonded in place and aligned we began the moulding of the sheets for the body, these were to be made from polyester resin on the outside and have a ply lining on the inside, and the void filled with an expanding insulation foam. This would form our own highly insulated SIPS panelled body capable of operating in high or low temperatures, and would take minimal heating or cooling in extreme temperatures, and lower fuel costs for heating and electrical consumption for the air conditioning. Highly insulating expanding foam has great adhesive qualities and would bond to the outer glass fibre body and the inner Lite-ply lining to form a single structural panel, and give excellent thermal efficiency.
Making the body panels began with making a perfectly flat surface on which to mould them as they were to be made to their full length and width; they were to be made slightly oversize so they could be trimmed with a router for perfectly square edges. Two sheets of industrially sized plywood were obtained which were 11’ (3.35M) long, and 5’ (1.52M) wide, these were fastened to solid wooden bearers to give a total length of 22’ (6.7M) long.
With the sheets fully screwed and bonded to the bearers the screw holes and gap between the sheets were filled and sanded flat, any other surface perfections on the plywood sheet assembly were also dealt with and sanded flat so it had no surface imperfections. Any imperfections would show up as the wooden assemblies plywood sheets were to me used as the front face for our mouldings when we made them. The whole assembly was painted with several coats of epoxy varnish and sanded between each coat to ensure no perfections were present, and then it was covered with an industrial plastic which was pinned to it and tensioned so it had no ripples. This was polished with several coats of silicone free wax and buffed; two wooden sides were made and covered in cling film, then screwed to our assembly.
With everything ready we sprayed the whole assembly with PVA release agent, and then began moulding; we painted one coat of polyester resin directly onto the prepared plastic, let it harden, then applied another coat, being warm meant it went off in about 5 minutes. One long piece of moulding tissue was cut to length, placed on the hardened polyester resin, then coated with more polyester resin which was worked in so it thoroughly wetted it out, once hardened this process was repeated with another coat of tissue to give us a thin and pliable side. This was all done in one day and it was left overnight to fully cure, the sides were unscrewed and removed and the plastic sheet was removed complete with sheet of resin. New plastic was applied to our mould and the sides recovered with cling film, they were reattached, and the process was repeated until we had made sufficient panels for our vehicle body, they were stacked and stored until needed.
Many vehicle bodies are boxy and old fashioned and we wanted this to be modern and have large rounded corners for that modern look, so we looked to make another mould for these large rounded corners. Salvation came in a nearby carpet wholesaler who had massive cardboard drums on which his carpets came, he gave us several as they were 7 metres long and had a 300mm internal diameter.

These cardboard tubes were carefully cut in half lengthways and their cut edges were sanded until smooth, they were coated on the outside with several layers of polyester resin to stiffen them, and we added some gussets to further stiffen them.
Catering cling film was stretched along its length and it was worked into the inside of the half tubes to ensure there were no ripples, then two more pieces were added to give a thickness of three layers, these were sprayed with PVA release agent. These mouldings were made in the same way as our large sheets, two coats of polyester resin, two more coats with tissue, but as they were corners we added another coat of resin with CSM (chopped strand mat) which is thicker and stronger than tissue.
Having a number of tubes meant we could mould all these corners in one day, and once again these were left overnight to cure fully. These were left in their tubes as they needed cutting in half lengthways to give us 90 degree bends and not the semi-circular pieces we had, they were marked and cut in half in their tubes, with a bandsaw.

Several mouldings were needed for the various intrusions into the vehicle and were made by making a plug and using casting plaster to make the moulds, these were obviously identical and all the mouldings were made in one session. These mouldings were much stronger then the body mouldings and were made in the same way as the other mouldings, but, had four additional layers of the heavier CSM applied to give the additional strength.

With all the fibreglass mouldings made it was time to fit them, the side panels all had one side and end trimmed with a router and track, but fitted with a diamond cutter bit for a better and smoother finish than tungsten tipped bits. This ensured that each panel had one square edge or 90 degree angle to act as a datum or reference point.
Each panel was offered to the vehicle individually, these were the two lower panels of the outside first, they were measured, the measurements checked, marked, and the markings checked, then they were cut with the router. Each panel was offered up to the vehicle again and the wooden skeleton framing was marked for easy alignment of the panel, the side of the floor SIPS panels and sides of the wooden framing were liberally coated with epoxy adhesive, and the panel fitted and clamped. After 2 hours the epoxy was fully cured, and both lower outer side panels were fitted, and the rest were left off to allow the internal fitment to take place. Inner linings were to be 3mm thick Lite-ply, this was temporarily fitted at the lower edge of each side using panel pins, the purpose was to allow the wooden plinths for equipment to me made, and the vehicle fitments to be installed in their final positions. With this done all the interior panels were marked to allow any vents or flues to be accurately installed, and the internal fitments were removed along with the mounting plinths. CSM was cut and an overlap for it to run into the wooden skeleton which allowed three coats of CSM to be bonded in and coated in polyester resin to thicken and stiffen the lower side panels, this was allowed to cure, and this bonded the full thickness side panels to the wooden skeleton.
With the lower panels installed and fully bonded in, and bought up to thickness, the next job was to install all the flues in the cavity, all the cutting and drilling of the lower part of the wooden framing was done. Everything to be installed in the cavity was installed; the Lite-ply internal lining was fitted to the lower parts of each side and permanently bonded in using epoxy. With this done and the lower panels were fixed in position polyurethane expanding foam was mixed in 1L batches and poured into the cavity, this expanded to 20 times its size so 1L would expand into 20 litres, and filled all the voids to form a highly insulated SIPS panel. This was poured in slowly to allow it to expand to just below the top of the fitted panels, both external glass fibre, and internal Lite-ply as this would allow room to join the next outer and inner panels.

Next the floor was marked out for all its wiring and heating pipe conduits to be installed, the various datum points had been marked while the various pieces of equipment was temporarily fitted, and these were used as reference points for the under floor installation. Channels were then routed out using a router and the various cable trunking was installed to hold the wiring; and the grooves for the hot water heating pipes and diesel pipe conduits.. Everything was installed in its final position and the grooves were filled with compatible expanding foam so it bonded to the SIPS floor panels, and the grooves were routed back to level so the 6mm ply could be replaced. With the plywood replaced we painted then in various colours to identify which service ran where in the floor if ever there was a problem; particularly as they were nearly all run in the floor, under the plinth which
Was to be used to mount all the equipment on.
The plinth was installed and some of the equipment was permanently installed, this allowed for accurate marking out of pipes for the sink and diesel water heater, the floor was drilled and plastic sleeves installed, the water pipes were installed and the gaps filled with expanding foam.

The rest of the outer body panels were installed except for the roof panel, rear, and any cable trunking and air ducting was installed, the panels were laid up with polyester resin as the lower side panels were to ensure they were to thickness, and fully bonded to the skeleton. Much of the inside Lite-ply lining was installed and the cavity was filled with expanding polyurethane foam to fully insulate it nearly up to roof level, and any fittings were installed as this progressed. The final roof panel was installed and had holed drilled to allow the cavity to be filled with polyurethane expanding foam from the outside, this too was fully bonded in and laid up with polyester resin and CSM to bring it to its final thickness. The final roof lining was installed and bonded in and all the lights were installed, and with this done the cavity was filled with polyurethane expanding foam to form the SIPS panel construction, and insulate it.

We now had a fully fabricated vehicle body which was essentially one large SIPS panel, highly insulated, and weighed in at only 42Kg’s, it was very flexible to deal with the flexing of the vehicle over rough terrain, and would need little heating or cooling.

Part 2 too follow.

Assassin